The invention relates to cooking or heating apparatus and, more particularly, to an improved tunnel oven and method for heating food products and the like by conveying them through the tunnel within a preselected time.
The invention is concerned specifically with tunnel ovens of the type wherein such food products are cooked by the absorption of infrared radiant energy which is emitted directly from the very walls, such as the roof and floor of the tunnel.
Is has previously been known to utilize infrared radiation for heating of food and other products by providing heating of the tunnel surfaces by means of infrared emitters such as of the type disclosed in coassigned U.S. Pat. No. 3,809,859 of Harold D. Wells, entitled "Infrared Emitter". Ovens of the type utilizing such emitters of tunnel character is disclosed in coassigned U.S. Pat. Nos. 4,008,996 of Harold D. Wells, entitled "Multiple Tier Oven", and 4,245,613 entitled "Tunnel Oven".
Ovens of the type using infrared emitter panels as described above do not heat articles by heated air, whether confined, forced or otherwise, except incidentally, nor do they utilize red-hot glowing wire or ribbon elements or quartz units. Rather, the infrared radiation utilized is typically of a lower temperature than such elements, inasmuch as the surfaces of the tunnel itself, whether the hearth or roof, provide large "black body" sources of infrared radiation for absorption by the food products. Such infrared tunnel oven provides cooked food products which have increased moisture retention than to reduce shrinkage, thereby providing a food product which is of attractive appearance and is a delectation for the customer.
When tunnel ovens of the present character are utilized for fast food service, wherein partially prepared or frozen foods of a wide variety must be heated for prompt serving, the tunnel oven must be capable of dealing with a wide variety of initial product temperatures, thermal absorption characteristics, thermal mass, ultimate serving temperature, requirements for browning or other finishing of the product, as well as other characteristics and parameters peculiar to the type of product to be heated. It will be recognized, for example, that heating and serving of fish fillets requires a processing time and heating profile which are different from those required for preparation of a thick cut of beef, etc. The problem is rendered difficult not only by the wide heating and temperature requirements of the food products to be cooked, but also by different requirements in cooking time, which will depend upon the rate of speed at which products are conveyed through the tunnel oven by a conveyor. Therefore, cooking of a wide variety of food products in such a tunnel oven requires consideration of a time-versus-temperature relationship which is unique to the food product being cooked.
Heretofore, conveyorized tunnel oven cooking equipment typically has utilized a single zone of heating in which a single temperature is maintained throughout the entire cooking process. This requires a longer time to bring food up to its ultimate cooking temperatures and in many cases compromises quality. Although it has been proposed to provide different zones longitudinally within conveyorized cooking equipment, such arrangements have not been utilized in a "black body" type of tunnel oven of the present character wherein the internal surfaces of the oven themselves act as the sources of infrared radiant energy. Nor have such multiply-zoned cooking arrangements addressed the problem of coordinating the cooking time, as brought about by controlling the speed of the conveyor, in a precisely coordinated relationship with the temperatures in the various zones in order to bring about a desired cooking profile for a specific food product.
It is an object of the present invention to provide an infrared tunnel oven for flameless, electric cooking of food products by the direct emission of infrared radiant energy from surfaces of the cooking tunnel wherein there are provided a plurality of heating zones, in each of which the infrared source temperatures can be independently maintained electronically by an electronic control circuit which, at the same time, also precisely controls the speed of a conveyor extending through the tunnel to provide conveying of food products along the length of the tunnel within a predetermined cooking time.
It is a further object of the present invention to provide a tunnel oven of the character stated which utilizes microprocessor control not only of the temperature in each of plural zones but also the speed of a conveyor extending through the tunnel oven for causing the food products to be conveyed through the length of the tunnel within a preselected cooking time.
It is a further object of the present invention to provide a tunnel oven of the type stated which allows user selection of different top and bottom temperatures within each of the plural cooking zones; which provides a continual read-out of all temperatures within the different zones; which includes provision for causing automated operation of functions including automatically turning off and on at particular times and dates which allows automatic self-cleaning to be initiated; which provides a stand-by mode in which electrical energization of heating elements is reduced for purposes of economy during slack periods.
It is another object of the present invention to provide a tunnel oven of the character stated which allows for the use of a cooking profile of food products within the tunnel oven for bringing about a major reduction in the cooking time of various food products so as to improve productivity, reduce energy costs, minimize cooking mistakes and food losses, and reduce floor space heretofore required for equipment.
It is also an object of the present invention to provide such a tunnel oven which saves labor and increases productivity; which reduces the need for highly skilled kitchen and maintenance personnel; which cuts employee training costs; and which reduces ventilation and air-conditioning costs.
A further object of the present invention to provide a tunnel oven of the type stated which has suitability for widespread usage for all sorts of institutional, industrial and commercial purposes; and which is highly reliable and long lasting in such use.
An object of the present invention is also to provide a tunnel oven of the character stated which can be configured in multiple tiers, stacked one above the other in compact disposition, wherein each such tier provides its own multiply-zoned tunnel wherein the cooking time, temperatures, and other aspects of operation of each such tier are independently controlled.
A still further object of the invention is to provide a method of infrared cooking of food products by use of a tunnel oven such as will achieve advantageous profiled cooking of the products in a reduced time and yet such as will produce a more suitable, delicious food product.
Briefly, an infrared tunnel oven for flameless, electric cooking of food products by infrared radiated energy includes at least one tunnel oven tier defining a cooking tunnel having an entrance and exit at opposite ends. The oven includes a base for supporting the tier (or tiers) for horizontal disposition of the tunnel in each such tier. The tunnel is divided along its length into at least two heating zones. The tunnel includes a roof as well as a hearth defining a floor over which a conveyor belt is driven electrically to convey food products through the tunnel. Independent electrical heating panels are utilized for separately heating the roof surfaces as well as the hearth within each zone to preselected top and bottom temperatures, respectively, for direct emission from the roof and hearth of infrared radiant energy into the tunnel for absorption directly by the food products as they are conveyed through it. The motor-driven conveyor is of continuous belt construction, being speed-controllable. A control circuitry for each tier includes microprocessor-controlled circuitry including provision for user preselection of top and bottom temperatures in each zone, as well as preselection of the cooking time, i.e., the time during which food products will be conveyed through the length of the tunnel. Such circuitry measures the top and the bottom temperatures in each zone, under microprocessor control, bringing about automatically the control of the electric heating panels to maintain substantially the preselected top and bottom temperatures in each zone. Also, the same microprocessor circuitry controls the speed of the conveyor to cause the food products to be conveyed through the length of the tunnel within the preselected cooking time. Accordingly, according to such apparatus and its novel method of use, the food products may be rapidly, accurately and uniformly cooked by being differentially heated in the different zones, to produce profiled cooking while they are conveyed through the zones in a precisely time-controlled manner.
Other objects and features will be in part apparent and in part pointed out hereinbelow.